The manufacture of such structures began more than forty years ago, and the demand for them and the pursuit of solutions to the needs and objects of their application have spawned a large number of both designs and of producers. James Thomas Engineering, Tomcat, Tyler, Total, xTreme, Prolyte, and Applied are only a few of the producers.
Many such trusses are rectilinear in section, often in what have become defacto standardized cross-sections/dimensions (e.g., “12×12” and “20.5”). Loads of various kinds, including lighting fixtures, are attached to, hung from, and/or supported atop such trusses, which are supplied in a variety of standard lengths, as well as with corner blocks and hinges for joining two or more lengths at fixed or variable angles.
Portable lighting systems have long been employed in which the fixtures are shipped separately from trusses and then are temporarily attached to the trusses at the venue; attached individually, or with the fixtures having been previously mounted together in groups to a shared intermediate elongated support (a “lamp bar”) which, in turn, is attached at the venue to the truss or other supporting structure.
There have also long been a family of truss designs adapted such that the loads supported (typically lighting fixtures and some of their associated wiring and accessories) can be shipped already pre-installed within the truss structure, so as to reduce the amount of time and labor required at the venue to convert the equipment from the form in which it is shipped, to that required for its use.
In one subclass of such trusses, often referred to as “box” trusses, the fixtures remain fixed entirely within the envelope defined by the truss's exterior members, protecting the fixtures in shipping by employing the truss structure itself as a shipping crate. Because the fixtures remain so enclosed during use, the truss's structure is minimized on one (and sometimes at least part of a second) side to reduce obstructions to the light beam they produce. Internal mounting still reduces the range of angles through which the fixture can be physically adjusted in a truss of reasonable size. An example “box” truss is seen (on a smaller scale) in U.S. Pat. No. 5,743,060 to Hayes et al.
Another subclass of trusses employing the truss structure as a shipping crate mounts the fixtures to an intermediate elongated support (“bar”), which can then be displaced within the truss between a shipping position (in which the fixtures are contained entirely within the structure) and a use position in which the fixtures are substantially exterior to the truss structure; dramatically increasing the range of angles through which the fixtures can be adjusted on site without obstruction of the fixture or its beam. Such “pre-rig” truss became a popular solution in the 1980s, when such lighting fixtures were the well-known PAR-64 fixture (one generally similar to FIG. 13 of U.S. Pat. No. 3,116,022). The minimal weight of an aluminum PAR-64 fixture allows a typical “lamp bar” of six such fixtures to be displaced between its shipping and use positions by hand, although motorized and cable/spring assisted versions were seen.
In the case of “automated” lighting fixtures (as disclosed in U.S. Pat. No. 3,845,351 and as widely adopted over the last quarter-century), their appeal is, in part, a reduction in the number of fixtures required to produce a series of lighting effects and, thereby, in time and labor—a benefit that is eroded if the fixtures require separate shipping and individual handling.
Automated fixtures are also vastly more complex. Handling them increases the prospect of damage.
These factors require an approach to pre-installing that is suitable for automated fixtures, but neither the “box” nor the manual “pre-rig” solution, as employed for PAR64s, proved practical.
In the case of “box” trussing, making full use of an automated fixture's potential requires maximizing its range of possible pan and tilt adjustment without obstruction of the fixture or its beam.
In the case of “pre-rig” designs, manually lifting and lowering automated fixtures weighing between 30 and 90 pounds (versus only a few pounds for a spun aluminum PAR-64 fixture) between use and storage positions is impractical.
U.S. Pat. No. 5,278,742 to Garrett is such a traditional “pre-rig” truss effecting the displacement of the fixtures between shipping and use positions using motors installed in the truss itself—increasing cost and complexity and requiring access to AC power for operation.
Another displacement method inverts the process, employing the “muscle” of the chain motors or ground support that will lift the structure to displace the truss structure, relative to the fixtures and their intermediate support, between internal shipping and externalized use configurations; the fixture weight typically born by the floor surface during the transition by wheeled temporary supports, which will then be removed or retracted. Examples include U.S. Pat. No. 5,335,468 to Oberman.
A different approach reconfigures the truss structure itself. Employed in 1987 by Morpheus Lights and disclosed in U.S. Pat. No. 4,862,336 to Richardson, it was an adoption of a truss design introduced years earlier in a PAR-64 version by Michael Tait of Tait Towers. In such designs, the fixtures are “moved” relative to the truss structure by mechanically reconfiguring the truss itself around the fixtures and their immediate support; changing between a fully enclosing shipping configuration and a different “use” configuration in which the fixtures have been, in effect, displaced from the inside of the truss to outside it (the end states illustrated in FIGS. 2 and 4 of Richardson). During shipping and the conversion process, the weight of the structure and of the fixtures is borne by wheeled temporary supports, which are removed before fixture use.
A variation was later introduced by Tomcat Global as the “Swing” truss, whose wheeled temporary supports are both captive and retracted.
Several of these truss designs, in their use configuration, produce a U-shape in which a catwalk is provided, enclosed by two side panels.
Less complex is another type of pre-hung truss, whose precursor was also first used with un-automated fixtures. In this type, a shallow rigid truss is employed having one side (nominally the bottom) from which at least the working end/head of the fixture protrudes. This affords a wide range of angular beam adjustment in use, although the reduced height of the side panels of the permanent truss structure reduce its strength, for a given construction, reducing the allowable span between supports. Protective enclosure of the fixtures in shipping is provided by a separate wheeled frame for each section that supports the permanent portion and surrounds the otherwise exposed parts of the fixtures attached to it, protecting them in shipping.
In one early example, the added protective enclosure comprised, in effect, a wheeled framework or open-sided bin, atop which an associated truss section would ride. One disadvantage of this approach is the volume of space demanded to store such rigid enclosures while the truss is in use.
U.S. Pat. Nos. 8,517,397 and 8,757,641 to Gross and employed by Production Resource Group, the industry's largest provider, illustrate another variation. Here, the enclosing frame or dolly used in shipping can be folded into a smaller volume, at the cost of its greater complexity, weight, cost, and of the additional operations required to fold and unfold it.
Another of the industry's largest providers, Christie Lites, has its own variant, generally disclosed in U.S. Pat. Application 2013/0075993 A1, in which a similar pre-hung truss 110 is shipped atop a “trolley” 100. As manufactured for Christie, the trolley sides fold.
All such approaches suffer from requiring alignment between the permanent truss and its frame/dolly at each and every section in a span for the former to be landed safely atop the latter after use, in preparation for shipping.
Another approach, as disclosed in U.S. Pat. No. 8,099,913 to Dodd and sold by Tyler Truss of Pendleton, Ind., further simplifies by supporting the permanent portion of the shallow permanent truss and enclosing the fixtures suspended in it using two U-shaped, largely planar wheeled frames (“carriages” 50 and 51 in that specification), whose vertical members (e.g., 52, 53) are accepted by and retained in sleeves or tubes 37-40 installed in the corners of the permanent truss portion. Horizontals (e.g., 54) of the carriages protect the fixtures; stiffen the verticals; and can be used in fork-lifting the truss section. The carriages, once disconnected from the truss (after it has been lifted sufficiently off the floor), can be stored separately or can be inverted and re-inserted in the other/upper end of the sleeves 37-40, as is illustrated in FIGS. 6 and 7, serve as handrails.
Simple in principle, the structure of Dodd and its implementation as the Tyler GT, although widely adopted, presents many unresolved practical difficulties that cost valuable time and complicate its use.
For one, tight tolerances between the diameters of the leg verticals (e.g., 52 and 53) and the receiving sleeves/tubes 37-40 result in binding during leg insertion and removal when the two workers necessary (one at each end of the same carriage) do not synchronize their movements.
The vertical legs offer a plurality of pass holes 61 for the insertion of a locking pin 63 captivating the leg in the sleeve, so as to permit the selection of different carriage heights, depending upon the vertical extension of the fixtures or other loads attached in the truss. Workers might (without a clear marking or accessory mechanical stop) insert and pin a leg not in the correct hole, differing from end to end of the same carriage; from side to side of the same truss section; or from section to section of a continuous series/run of sections. The need for rework and delays result.
The centerline of the Dodd/Tyler carriage horizontal (e.g., 54) is offset from the centerline of the sleeves 37 and of the leg verticals in order to bring the horizontals into the same plane as the elongated chords (e.g., 24 and 26) of the truss section during transport. When the leg carriage is simply inverted, that offset is subtracted from the leg/sleeve spacing across the centerline of the truss, such that the clearance between inverted carriage horizontals is reduced to less than the sleeve spacing, and can be insufficient for typical chain motors and rigging used to suspend the truss, as well as making it difficult to pass them. In such cases, providing adequate clearance requires that the leg carriages, which in the case of a 10′ model weigh 65 pounds, must not only be inverted but also reversed end-to-end, costing further time and effort.
Inverting the carriage for storage/handrail use is not always practical or desirable for reasons of appearance; limited clearance above; or the difficulty that the carriage verticals present to access to the top surface of the structure, including for operations such as stringing cables along its length. In such situations, the carriages must be collected and stored, in piles on the floor; inserted leg-down in pairs of emptied roadcases/shipping crates used for cable or other purposes; or inverted racked on a pair of castered storage dollies supplied by the manufacturer (which dolly itself is inconvenient to handle, use, ship).
The objects addressed by the instant disclosure include more efficient approaches to the thirty-year pursuit of a “pre-hung” solution for automated fixtures, as well as addressing the practical difficulties presented by the Dodd/Tyler approach to the challenge.
Further objects include improvements to trusses designed for more general use, and for the shipping of a truss having a novel cross-section, as previously disclosed by the applicant, in a manner that cooperates with that of pre-hung truss.